1. Field of the Invention
The invention relates to a process for homogenizing essentially immiscible liquids for forming an emulsion in which the inner and outer phases are dispersed under pressure, as well as to an apparatus for performing the method.
2. Description of the Related Art Such a process is known, for instance, from U.S. Pat. No. 4,533,254. A so-called raw emulsion or crude emulsion is first formed in that process for forming an emulsion from two essentially immiscible liquids (e.g. oil and water). The two liquid phases are fed to a premixer and premixed therein, for example by stirring. The premixed liquid thus obtained is then subjected to very high pressure. The pressure depends on the respectively employed inner (dispersed) phase (up to 1,400 bar) because, for dispersing the inner phase into the outer phase, a very large amount of energy is necessary in order to overcome the attractive forces among the particles in the inner phase for the purpose of breaking up the particles. The attractive forces in the inner phase are considerably greater than in the outer phase. The entire raw emulsion is thus pumped to a separation pressure necessary for the inner phase and then very suddenly expanded whereby, in the process according to U.S. Pat. No. 4,533,254, the raw emulsion is divided into two partial streams and collided counter-current in thin sheets from mutually oppositely disposed nozzles. Due to shearing effects and cavitation, the liquid droplets are disintegrated and intensively mixed in the exciting turbulent current.
The known dispersion method therefore requires a substantial amount of energy, since the entire pre-mixed raw emulsion must be pumped to a pressure necessary for the inner phase. Usually, however, the inner phase is only about 5 to 20% of the entire mixture, so that the substantially greater share of the expended energy is applied to the outer phase. This leads to a corresponding great energy loss and also to a substantial warming of the mixture, which is disadvantageous for heat sensitive mixtures. A further disadvantage of the known processes lies in the fact that they can operate only discontinuously, because it is necessary to produce a raw emulsion in a suitable mixing container prior to the actual dispersion.
A process for mixing flowable media is described in Swiss patent CH-PS 363 968, in particular for producing carbonated water. The paper does not disclose a homogenization process for forming an emulsion, the object is instead to finely distribute a gas in a liquid, whereby the two fluids are first oppositely led in a mixing chamber at slightly different pressures and then they are mixed in a further stage.
Other solutions are known, for example, from international application PCT/WO 89/07007, from German published, non-prosecuted applications DE-OS 20 23 862 and DE-OS 26 51 433, and from German patent No. DE-PS 401 474.
It is accordingly an object of the invention to provide a process and an apparatus for homogenizing essentially immiscible liquids for forming an emulsion, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known processes and devices of this general type and which makes possible the production of an emulsion from two essentially immiscible liquids continuously and with substantially lower energy consumption as compared to the prior art processes and apparatus.